Define "ground effect" as it pertains to aircraft.

Ground effect refers to the aerodynamic phenomena that occur when an aircraft is flying close to the surface of the earth, typically within a height of about one wingspan from the ground. When an aircraft is in this position, the airflow patterns around the wings change, resulting in increased lift and decreased drag.

This occurs because the presence of the ground interferes with the downwash of air behind the wings that typically contributes to drag. As a result, the aircraft experiences a cushion of air that enhances lift, making it easier for the aircraft to remain airborne and requiring less power to generate lift. This effect is particularly noticeable during takeoff and landing, where pilots can utilize it to aid in achieving effective flight performance.

Understanding ground effect is crucial for pilots, as it influences how they manage takeoff and landing phases, especially regarding the aircraft's approach and flare. Recognizing this phenomenon also helps pilots to avoid potential issues, such as floating during landing or misjudging the clearance needed for safe takeoff.